Project Summary: The ISWI type chromatin remodeling complexes have been shown to be involved in transcription repression, and the regulation of transcription elongation and termination. Reorganization of chromatin and regions in chromosomes are fundamental in cellular development and differentiation. We propose to further our understanding of these processes by a two-prong approach of (1) extensive biochemical characterization of the ISWI family of proteins and (2) the molecular genetic analysis of mutant versus wild type ISWI complexes in vivo.